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Machinegun Practicalities


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#1 Marek Tucan

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Posted 09 July 2017 - 0826 AM

Hello, 

 

Few layman questions about machineguns of all sorts:

 

 

1) What are the typical rates of fire based on role?

Looking at some US field manuals I can see something like:

M249:

Sustained RoF 50 rounds / minute (3-5 round bursts)

Rapid: 100 rpm (8-10 round bursts)

M240:

Sustained 100 rpm (6-9 round bursts)

Rapid 200 rpm (10-13 round burst)

M2:

Sustained 40 rpm (6-9 round burst)

 

 

How would that look for the older machineguns? The M1919's, the water-cooled machineguns? For magazine-fed light machineguns?

 

 

2) With machineguns with adjustable rate of fire: When/why is it done? Would say a MG-3 be adjusted for 1,000 rpm for light machinegun role and to 1,300 for a vehicular mount? As far as I recall for MG-42/MG-3 this is done by changing the receiver, so probably needs to be done on depot, but for M-249 or FN-Mag this can be done without changing any parts? And what application would call for the higher "setting"?

 

 

 



#2 Richard Lindquist

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Posted 09 July 2017 - 0900 AM

There was a Brit machinegun company in WWI with water-cooled Vickers that fired some god-awful number of rounds over a certain period without any non-clearable stoppages.  There isn't a gun built today that will do that.  Those WWI machineguns were carefully machined and forged whereas modern machineguns use a lot of stampings to ease production and save weight.



#3 Chris Werb

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Posted 09 July 2017 - 0914 AM

Arguably the FN MAG is well over engineered. The bolt locks at the rear, meaning the entire receiver, back to the locking lugs is load bearing leading to unnecessary weight. This was known about with its forbear the BAR which was to have been replaced with the much lighter, front locking Winchester Automatic Rifle. The PKM locks at the front, so its receiver is not load bearing. That must save a lot of weight.



#4 Marek Tucan

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Posted 09 July 2017 - 0954 AM

There was a Brit machinegun company in WWI with water-cooled Vickers that fired some god-awful number of rounds over a certain period without any non-clearable stoppages.  There isn't a gun built today that will do that.  Those WWI machineguns were carefully machined and forged whereas modern machineguns use a lot of stampings to ease production and save weight.

to my understanding that was a pre-planned indirect fire mission, right? My question is more how would they fire in "normal" circumstances. 

 

This is not really a question about specific designs - rather about specific roles...



#5 Tim Sielbeck

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Posted 09 July 2017 - 1055 AM

The M-85 .50 caliber had a switch on the back plate.  High rate, 625 rpm, was for aerial targets, low rate, 400 rpm, was for everything else.

 

Odd thing.  I distinctly remember in basic, 1979, they told us the firing rates were 900/600.  I have a pdf of an M-85 manual from 1984 that gives 625/400.



#6 Marek Tucan

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Posted 09 July 2017 - 1124 AM

I guess also in AA fire you would be supposed to use longer bursts than against ground targets?



#7 Ken Estes

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Posted 09 July 2017 - 1227 PM

Depends whether you are the target of the aircraft or not!



#8 mattblack

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Posted 09 July 2017 - 1451 PM

If one built a water cooled MAG or PK,they too would probably fire for quite some period of time.

#9 Richard Lindquist

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Posted 09 July 2017 - 1801 PM

 

There was a Brit machinegun company in WWI with water-cooled Vickers that fired some god-awful number of rounds over a certain period without any non-clearable stoppages.  There isn't a gun built today that will do that.  Those WWI machineguns were carefully machined and forged whereas modern machineguns use a lot of stampings to ease production and save weight.

to my understanding that was a pre-planned indirect fire mission, right? My question is more how would they fire in "normal" circumstances. 

 

This is not really a question about specific designs - rather about specific roles...

 

As long as you keep replenishing the water supply, the water-cooled machinegun can keep on firing.  The water boils off and you just have to keep on refilling it.  If you can keep water and ammo coming, the firing can go on until you totally erode the rifling lands in the barrel.



#10 DKTanker

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Posted 09 July 2017 - 1943 PM

The M-85 .50 caliber had a switch on the back plate.  High rate, 625 rpm, was for aerial targets, low rate, 400 rpm, was for everything else.

 

Odd thing.  I distinctly remember in basic, 1979, they told us the firing rates were 900/600.  I have a pdf of an M-85 manual from 1984 that gives 625/400.

I think your PDF is incorrect.  On high rate I know from experience that the M85 fired every bit as fast as the M240.



#11 Tim Sielbeck

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Posted 09 July 2017 - 2138 PM

That's what I remember, too.  It is a pdf copy of TM 9-1005-231-10, the M-85 operator's manual.



#12 Colin

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Posted 09 July 2017 - 2316 PM

The Brits still practice indirect MG fire, Canada has let that skill set fade.



#13 Richard Lindquist

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Posted 10 July 2017 - 1019 AM

The Brits still practice indirect MG fire, Canada has let that skill set fade.

Trudeau won't give you enough ammo to try it.



#14 rmgill

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Posted 10 July 2017 - 1041 AM

As long as you keep replenishing the water supply, the water-cooled machinegun can keep on firing.  The water boils off and you just have to keep on refilling it.  If you can keep water and ammo coming, the firing can go on until you totally erode the rifling lands in the barrel.

 

Supply water, SAA, spare barrels, men to move the ammo and water, men to reload the belts, etc. 10,000 round life for a barrel....It's my understanding that there's a way to change the barrel without losing too much water. 

The guns ARE heavy for a reason. The parts are large and over built. 

The account of the 100th Bgd's MG Coy at High Wood, the target was an assembly area of the germans for their presumptive counter attack. Just short of a Million rounds fired....





#15 17thfabn

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Posted 10 July 2017 - 1042 AM

The Brits still practice indirect MG fire, Canada has let that skill set fade.


Artillery, mortars, rockets etc are much better for indirect fire. Indirect machine gun fire was found to be not very effective.

#16 Chris Werb

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Posted 10 July 2017 - 1210 PM

 

The Brits still practice indirect MG fire, Canada has let that skill set fade.


Artillery, mortars, rockets etc are much better for indirect fire. Indirect machine gun fire was found to be not very effective.

 

 

Exactly. I'd argue it could be somewhat effective but incredibly inefficient/costly compared to mortars in particular.



#17 Markus Becker

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Posted 10 July 2017 - 1614 PM

How would that look for the older machineguns? The M1919's, the water-cooled machineguns?


RoF of the plane mounted, air cooled .30 was 1,200 as opposed to well under 1,000 for the ground version.

#18 shep854

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Posted 10 July 2017 - 1958 PM

Speaking of...



#19 R011

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Posted 10 July 2017 - 2213 PM

 
How would that look for the older machineguns? The M1919's, the water-cooled machineguns? For magazine-fed light machineguns?

When the Canadian Army switched from the M1919 to the MAG, we were taught to use the same number of rounds per burst with the same pause between bursts with the new weapons as with the old. This meant effectively the same rate of fire. As far as I recall, the cyclic rate for the two weapons was either the same or so close as not to make a difference, about 600 RPM. The only difference is that the old 1943 vintage weapons tended to have a much greater number of stoppages than the new ones.

#20 Colin

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Posted 10 July 2017 - 2308 PM

 

The Brits still practice indirect MG fire, Canada has let that skill set fade.

Trudeau won't give you enough ammo to try it.

 

nah, mostly it's not cool with the new kids, all "old stuff" that does not fit the COIN warfare ops. Wait till they get sent to  Korea.....






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